1. Field of the Invention
This invention relates to a liquid medicine injecting device for feeding a liquid medicine stored in a liquid medicine receiving portion and, more particularly, to a modification of a known device for controlling flow amount of the liquid medicine when feeding the liquid medicine into human body.
2. Description of the Related Art
The liquid medicine injection into the human body has previously been conducted manually or automatically by a syringe storing therein the liquid medicine through a needle or catheter or by a drip-feed solution instillator.
The use of such a conventional device needed several minutes or hours for both a patient and a doctor or nurse the condition of which causes the patient to feel pain because of long injection period of time or to remain still and the doctor or nurse to hold the syringe long time or to check drip-feed amount.
There were some prior arts regarding to liquid medicine injectors which do not require the patient and the doctor or the nurse to remain still and provide a preferable handling because of small in size (cf. Japanese Patent Laid-open No. Sho56-102252, Japanese Patent Publication NO. Hei61-51901, Japanese Patent Laid-open No. Sho62-11465, and Japanese Patent Laid-open No. Hei2-307477).
Most of these conventional liquid medicine injectors included an elastic balloon to store therein the liquid medicine one end of which is used as an inlet to allow the liquid medicine flow into the balloon and the other of which is used as an outlet. The inlet of the balloon is provided with a leakage preventing system defined by a check-valve regulating the flow of the liquid medicine in one-way and a partition made from a soft rubber.
The balloon is intended to flow out the liquid medicine stored therein from the outlet when it deflates to supply the liquid medicine into the human body through a needle as a human body fitting tool.
However, it has been understood that the outlet of the conventional liquid medicine injector did not work well as a member for controlling flow amount in practical use.
Taking for an instance, the flow amount control system for liquid medicines in Japanese Patent Laid-open No. Sho56-102252 employs a short length pipe the inner diameter of which is changeable. But, such a short pipe was not preferable for precise flow control.
The flow amount control system for liquid medicines in Japanese Patent Publication No. Sho61-51901 employs a diaphragm which can change a diameter of inlet hole provided in a pipe wall of a cylindrical body where a balloon is attached and further can change an area of outlet inner diameter of the cylindrical body in response to the inner pressure of the balloon.
However, it was known that the inlet hole provided in the pipe wall was not thick to control flow amount and the diaphragm was not produced easily in practical use.
The flow amount control system for liquid medicines in Japanese Patent Laid-open No. Sho62-11465 employs a flow amount control wringable valve at the outlet. But, this is still impossible to precisely control flow amount.
The flow amount control system for liquid medicines in Japanese Patent Laid-open No. Hei2-307477 employs a thin tube inserted in a liquid medicine receiving portion to control flow amount. The thin tube was generally made of a stainless or glass tube having the diameter of 0.05 mm, but involved the following problems.
When one considers to control flow amount by utilizing a thin tube, the tube should have the inner diameter of 0.05 mm, the outer diameter of 0.020 mm and the length of 1000 mm under a 1400 mm water column to obtain the constant flow of 0.5 ml/hr. But, such a tube can not be obtained easily and is not metired in handling.
These stainless thin tube can be made of a drawn tube, but the drawn tube generally involves burr on the inner wall surface thereof which is not preferable for obtaining precise flow control.
When the hole diameter of the stainless steal thin tube will become lower than 0.05 mm, the outer diameter thereof may become 0.1-0.15 mm which is too thin to connect other members such as a liquid medicine tube, a filter and a main body. If desired to use the thin stainless steal tube, it will be available to be used after increasing the diameter but it requires to coat the tube.
When using a glass tube, it is too hard to be curved as the stainless steal thin tube so that the preferable length of the glass tube should be until 100 mm. It is therefore necessary to make the area small in size but which may cause difficulties in manufacturing.
Further, the material is tend to be broken easily in handling. The glass tube does not have an elastic property and is weak in shock so that the assembling thereof should be careful.
As has been described above, the glass and stainless thin tube can not be manufactured easily and does not have a large outer diameter to obtain 100 micrometer inner diameter.
The purpose of the present invention is to provide a liquid medicine injecting device capable of controlling flow amount precisely with a simple structure as described below.